Abstract
We studied the ventilatory response to hypoxia in 7 newborn kittens (n=12), 2 to 28 days old. Kittens were surgically instrumented to record diaphragmatic EMG (EMGDi), eye movements (EOG), electrocortical activity (ECoG), and neck EMG. Ventilation (VE) was measured with a mask and a flow-through system. Kittens inhaled 21% O2 for a control period of at least 2 min, 10% O2 for 10 min, and 21% O2 for 2 min again. Measurements were made in quiet sleep. With a decrease in FiO2 to 10%, there was an immediate increase in VE (0.210±0.017 to 0.300±0.025 L/min/kg; p<0.005) which was not sustained, ventilation decreasing to 0.224±0.028 by 10 min of hypoxia. VT increased from 3.8±0.2 ml/kg to 5.0±0.4 (p<0.005) and then decreased to 3.9±0.2. Frequency increased from 56±4.0 breaths/min to 63±3 (p<0.02) and then decreased to 55±5. The changes in ∫EMGDixf followed those in VE. Kittens studied before 7 days of life had a more pronounced decrease in ventilatory output at 10 min of hypoxia than older kittens. Breathing pattern became irregular or periodic during hypoxia. On return to 21% O2 ventilatory output decreased abruptly due to apnea. These results suggest; 1) the hyperventilatory response to hypoxia in unanesthetized kittens is not well sustained with values at end of hypoxia close to control levels; 2) the biphasic response to hypoxia is primarily a function of frequency; 3) younger kittens are less able to sustain hyperventilation than older kittens. We speculate that the late fall in ventilation is due to a central mechanism affecting frequency.
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Rigatto, H., Weibe, C., Rigatto, C. et al. 1820 THE VENTILATORY RESPONSE TO HYPOXIA IN THE CHRONIC UNANESTHETIZED NEWBORN KITTEN. Pediatr Res 19, 414 (1985). https://doi.org/10.1203/00006450-198504000-01838
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DOI: https://doi.org/10.1203/00006450-198504000-01838